This is a development thread for the re-release of "'Mass Accelerator" parts.

These parts originally come from the Stanford Torus Mod, which reached version 0.6.1 for KSP 0.90 on Curse on February 20th, 2015 before apparently having its development dis-continued (you can find the old forum thread here). I thought it was *excellent* work with a lot of potential, and worth re-releasing to continue the parts' legacy (Stanford Torus' updates were already coming less and less frequently by the time I created this) and make them available to more players.

The mod was released under a CDDL-1 license, which allows anyone to "use, reproduce, modify, display, perform, sublicense and distribute" the content with or without author permission. The license requires that I credit the original author, and re-release the original source code: which is provided below...

However, this isn't just a cut-and-paste re-release. While the Mass Accelerator parts do achieve a purpose never realized before in KSP (a functional, part-based Mass Driver), they aren't very realistically balanced...

The original parts can only accelerate a 2.5 meter 12.5-ton rocket at roughly 2 g's, whereas the Mass Driver designs for the real-life Star Tram proposal could accelerate a 40-ton 2 meter wide, 13 meter long rocket at 30 g's... The original parts are also darn expensive, heavy (30 tons/piece), and have weak attachments to each other which tend to cause Mass Accelerator stacks to break apart under the acceleration they create...

Thus, from the first day I got my hands on the Mass Accelerator part, I went into the config and started making some modifications to make it more realistic. ORIGINALLY:

- I increased the acceleration to 11760 kN/s (30 g's on a 40-ton rocket), and increased electricity consumption proportionally (this still needs some re-balancing: the original author states in config-file comments that he aimed for 1 MW per 100 kN/s- which equates to 10% efficiency, but it actually came out to 1 kW per 250 kN/s, if 1 EC = 1 kW). This performance is based on the real-life StarTram gen-1 designs...

- I decreased part cost to a more reasonable+realistic level (12,500 funds per part instead of 185,000 funds per part- the new cost equates to the still astronomical figure of $92.74 million/section in 2015 dollars, using the convention of 1 Fund = $1000 1965 US dollars), and reduced the part mass to 10 tons/ring (reasonably accurate for real-life aluminum-based Mass Driver coils).

- I also increased the toughness of a stack of Mass Accelerators in various ways (such as by increasing the node size from 2 to 3- as the rings are roughly 3.75 meters in outer diameter, raising the Crash Tolerance from 7 to 9, and tripling BreakingForce/Torque values...)

The part-balancing has changes somewhat since (I'm sure you can find the math errors I made above if you look carefully), but anyways, the result is this: a functional Mass Driver part, that, while it still has a few bugs/quirks, works realistically in KSP.

Version 1.3.2 is now LIVE. Changes from 1.3.0 include the addition of a readme, NEW SIZES of the Mass Driver part (with internal diameters sized for crafts from 0.625 to 5 meters!), and adjustment of tech node assignments (moved back in the tech tree).

(For the curious- the rocket pictured above also utilized a parachute-assisted Space-X style recovery of the launch stage, and travels all the way to the Mun with its payload... The engines produce less than 1 g of acceleration at max throttle when the fuel tanks are full- hence why the rocket has gained barely 3 m/s of speed after climbing more than 3 km...)

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- The Mass Accelerator does not unlock until you reach Advanced Construction in the tech tree. It should always be available in Sandbox mode, however.

- The vessel accelerated by the Mass Accelerator part MUST be a separate vessel. The easiest way to position something appropriately on the launchpad is to launch the mass driver + rocket as a single craft with a separator-style decoupler between (one that doesn't remain attached to either craft), then fire the decoupler to break the two apart.

- The Mass Accelerator will only work on a craft within about 10 meters of the loading end of the device (unlike a real Mass Driver, it can't work in either direction by reversing the direction of the electric current), and must be "Armed" via the context menu before it can be set to fire. The craft must remain in range after the Mass Accelerator is armed, until it fires.

- The Mass Accelerator will tend to explode quite violently if the craft is not lined up straight, due to the vessel slamming into the interior wall of the Mass Accelerator during acceleration. YOU HAVE BEEN WARNED.

- The Mass Accelerator only can accommodate vessels up to about 2.8 meters in diameter, although I wouldn't risk anything much over 2.5 meters if I were you... (these things are EXPENSIVE to replace)

- The Mass Accelerator part obeys Conservation of Momentum! It *WILL* recoil if fired without being firmly anchored to the ground! This is actually a VERY USEFUL feature, though- you can set up a system of realistic Momentum-Exchangers in Low Kerbin Orbit, if you want, that steal the momentum of craft or debris you're de-orbiting (by firing them Retrograde), and transfer that momentum to other craft you're trying to boost to a higher orbit...

- Although not required, I recommend installing FAR with this mod, as it will allow a streamlined rocket to preserve more of its velocity from the Mass Drivers on the way up. A tall and well-designed 2.5 meter single-stack can EASILY have a terminal velocity of 700 m/s or more... (terminal velocity is normally the most efficient speed to ascend at from a Delta-V perspective)

- Kerbal Joint Reinforcement is also recommended. The stock KSP physics engine has a tendency to randomly shake large craft when they are loaded into physics (it's a fault of stock KSP, *not* this mod). This can be DEVASTATING to a 70-part stack of networked mass drivers weighing hundreds of tons held in place by Launch Clamps- so I recommend KJR to help prevent random launchpad explosions.

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whoa a working mass driver. was not expecting that on christmas but do you have pictures of it in the daytime please?

Merry Christmas! (depending on your time-zone)

I'll have to dig out some daytime photos soon. Considering most of my rocket launches are night-launches, though, I might have to take some new ones from my current save, which uses 64K Real Solar System...

RSS causes some *occasional* bugs with anything left on the launchpad when you exit phyiscs-range if your terrain detail isn't turned up, by the way. I suggest turning Terrain Detail to the highest setting you can tolerate CPU/RAM-wise to avoid this, as losing a Mass Driver stack to a physics bug could get QUITE annoying and expensive.

I also suggest installing Kerbal Joint Reinforcement, as it helps a bit with buffering the game's physics against some of the random motions upon loading that can simply decimate a 70-unit Mass Driver stack...

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My laptop had a little bit of an accident (I dropped it), and now it's not really very capable of running KSP without going wacky (or even running without random crashes).

So screenshots of daytime launches using the Mass Accelerators might take a little while (possibly until I get a replacement laptop). But, in the meantime, I still want to hear how this mod is working out for you guys. So feel free to post your progress reports here.

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The mod may or may not still be working in 0.90 with the files released. My latest test didn't work correctly- will be attempting to fix in the next week or so.

Re-compiling for 0.90 may be the way to go- but I've never really compiled anything before. Would anyone like to provide some pointers on how to do so, or help maintain this mod with me?

EDIT: The mod contains no .DLL files, so there is nothing that should need re-compiling. I don't know what the problem with the mod is yet, although I am trying to find out... Anyone who has greater expertise than myself (basically, any expertise at all) with modding KSP should take a look at this, and see if they can't give me a hand!

EDIT #2: This mod contains no .DLL files, but it SHOULD contain a single .DLL file I missed before (its name led me to believe it was referring to the Science Experiments from the Stanford Torus mod- but it turns out it *ALSO* has code for the Mass Accelerators). I'll see if that fixes the mod for 0.90. If not, I'll need to re-compile the .DLL for 0.90. This is a bit beyond my capabilities, so I would appreciate some help with this.

The problem you encountered was that the mod is not working in 0.90 yet (I am actively seeking somebody to help me fix it, as I don't know how- my "Recompile" comment was idiotic, as there is no .DLL anywhere in this mod, so nothing that could need re-compiling...)

If the mod *HAD* been working, when you right-clicked on the Mass Drivers you would have seen a "Power Level" tweakable slider- and once you detached the payload (it needs to be a separate craft) you would have seen the option to "Arm" on the Mass Driver, and then to fire after 10 seconds... (giving you time to switch back to the payload).

I would warn you though, these Mass Drivers follow Newton's laws- meaning that accelerating a payload will create some SERIOUS recoil. That tank-like thing probably would have exploded on the runway due to kickback without some sort of ground-pylons to better anchor it into the ground (Kerbal Attachment System provides those, by the way...)

Regards,

Northstar

- - - Updated - - -

It's ALIVE!

Turns out all that was missing was a .DLL file. I didn't catch it on my initial testing of the mod because I also, incidentally, had that .DLL installed for testing some of the other features of the Stanford Torus mod for a fork (I've been thinking about forking the long-term science experiments as well). But when I updated to 0.90, it was a fresh install (because the laptop I had been running 0.25 on broke), so...

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Glad things seem to be working -- I've definitely got this on my to-try list! FYI, it seems the source code is in the original StanfordTorus package, inside the not-quite-sensibly-labeled "plugintutorial1.zip".

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Glad things seem to be working -- I've definitely got this on my to-try list! FYI, it seems the source code is in the original StanfordTorus package, inside the not-quite-sensibly-labeled "plugintutorial1.zip".

Thanks for pointing that out! I've went and added the Source Code to Kerbal Stuff (I hope they're OK with pages just for source-codes), and a link to the page in the OP...

I had no idea the original mod author had packaged the source code in that! (I thought it was just some kind of tutorial for the Stanford Torus mod that went in KSP's Scenarios folder...) Maybe I should have more carefully investigated that folder before judging it by its title...

Regards,

Northstar

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As an interim compliance solution, I doubt anyone will object, but a dedicated development and collaboration site (GitHub is pretty popular) would be good to set up in the long run -- it makes managing revisions, issue tracking, collaboration, and similar stuff much easier. Since the plugin works as-is, it's not a big deal, but as KSP revisions continue to accumulate, the risk of something in this mod having to change grows, and when that happens, source and revision control will be your friend. Once that's done, you can set up the KerbalStuff page to point to that repository for the source.

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Northstar, could I ask you to kindly upload the sources to a github repository? It is not much more work, and would save me lots of time of explaining people why of of your kerbalstuff mods is in CKAN and the other not

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I'm seeing the same thing - was able to download the source without problem

Fixed.

Had to upload the file again- previously you could only download it through the Changelog tab for some reason...

Enjoy the awesomeness! Feel welcome to post your videos, screenshots, etc. here! I will be selecting the best ones for the first post of the official release thread (when there's been enough time to work out all issues, set up a Github page for the source code, etc.)

Regards,

Northstar

- - - Updated - - -

Do you need help?

I'd love your help FreeThinker!

I just got the mod working for 0.90, but I'll need help maintaining the mod if future revisions of KSP actually require a re-compile (luckily this one didn't), or if players find any bugs that I don't know how to fix...

Edited January 28, 2015 by Northstar1989

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Tested on a basic rocket. Currently after firing everything on the pad (driver, batteries, supports to hold it down) other than the object fired into the atmosphere is getting blown up. Pretty sure I'm doing something wrong. Mass driver definitely works though!

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Tested on a basic rocket. Currently after firing everything on the pad (driver, batteries, supports to hold it down) other than the object fired into the atmosphere is getting blown up. Pretty sure I'm doing something wrong. Mass driver definitely works though!

Most likely you just need to add additional struts and Launch Clamps to the mass-driver. Pictures would help me figure out your problem, though.

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Nice idea, ill give it a try and see if its better then my old way of making mass drivers out of rocket engines.

Now all we need are mass relays and the game is perfect!

That's a very KERBAL way of building a launch-assist system, though that's not really so much a Mass Driver as it is a Space Gun... Either way, whatever works for you- this way shouldn't consume any fuel for the initial boost though...

If by mess relays, you mean orbital mass driver systems, though- it's already possible with this mod. Just stick a stack of Mass Accelerators on top of a REALLY BIG ROCKET, and you can launch them to orbit (or, alternatively, just build them in orbit using the Extraplanetary Launchpads mod- Mass Drivers are little more than a coil of aluminum wire, and it's one of the few things I would say is *legitimate* to build in orbit if you only consider Kerbals to have modern-day technology...)

The Mass Accelerators work perfectly fine in orbit (in fact better, as there's no ground for the recoil to drive them into and cause them to explode...) and you can utilize the recoil force in clever ways to actually GAIN orbital velocity for the mass driver from de-orbiting debris, returning capsules and such- and then transfer this orbital velocity to a spacecraft bound for a higher orbit (or the Mun, or another planet) by boosting it in the prograde direction when at periapsis of the resulting elliptical orbit...

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EDIT 2: The Slug hit ~3400 m/s And was on an exit velocity aiming for deep space.

AWESOME. I didn't know it was possible to get a payload going that fast that low in the atmosphere with FAR installed (you *DID* have FAR installed, right?) without dynamic pressure crushing it like a tin can or causing it to rip itself apart...

As for the recoil, I'm not sure. It's definitely there (you can measure this with an unsecured Mass Driver built sideways on the runway), but perhaps it wasn't enough to overcome the static friction of those tank treads on the runway? Just how heavy WAS your firing station?

If it was more than a few hundred tons, it might not have been enough to move it (alternatively, maybe everything occurred too fast for physics to simulate recoil correctly- I've never launched anything that light at that high a power-level before...) Consider that each Mass Driver produces a force of 11760 kN/s at 100% power, and your firing tube was pointed at an angle above the horizon (meaning that much of the force was directed DOWNWARDS- further increasing static friction with the Runway). If nothing else, maybe there was some kind of a bug with the force not being transmitted throughout the craft based on the way the Mass Drivers were attached...

EDIT: On more careful inspection of the video, it does look like the firing unit lurches *very slightly* back, although it may just be my imagination... The heavier the firing station, the less the velocity-change it would experience, even without ground friction to hold it in place... Try utilizing a much LIGHTER firing station pointed purely horizontally if you want to see if the recoil is still working, or perhaps bugged for you for some reason...

Regards,

Northstar

Edited January 30, 2015 by Northstar1989

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AWESOME. I didn't know it was possible to get a payload going that fast that low in the atmosphere with FAR installed (you *DID* have FAR installed, right?) without dynamic pressure crushing it like a tin can or causing it to rip itself apart...

As for the recoil, I'm not sure. It's definitely there (you can measure this with an unsecured Mass Driver built sideways on the runway), but perhaps it wasn't enough to overcome the static friction of those tank treads on the runway? Just how heavy WAS your firing station?

If it was more than a few hundred tons, it might not have been enough to move it. Consider that each Mass Driver produces a force of 11760 kN/s at 100% power, and your firing tube was pointed at an angle above the horizon (meaning that much of the force was directed DOWNWARDS- further increasing static friction with the Runway). If nothing else, maybe there was some kind of a bug with the force not being transmitted throughout the craft based on the way the Mass Drivers were attached...

Regards,

Northstar

476.5 Tons. Far is on but I turned of aerodynamic structural failures as the slug would implode upon leaving the barrel (Making for a boring launch).